Last week, Bing was hit by a cache bug that showing third party content. That was an unusual bug that contains cache page results.
The Bing cache bug was not only showing the cache page that the user website contains but also the content from the third party sites.
Bing resolves the issue within 24 hours after the issue was reported to the company. The company said it was a bug, not a hack so there is nothing to worried about.
Tweet By The Company:
Thanks for reporting. We're aware of the issue that caused occasionally Bing cache page to display content from other pages. We are on top of it and rolling out a fix. Bing search Index and results are not impacted by this issue.
— Microsoft Bing Webmaster Team (@BingWMC) November 8, 2019